Soil stabilization method

ABSTRACT

A method of use of a composition for soil stabilization is disclosed. The composition comprises a solution of soluble sodium silicate applied at the disclosed application rate to improve the load bearing capacity for a roadway. The method of the invention addresses the application of the disclosed composition to maximize stabilization of road beds.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present patent application claims priority to U.S. ProvisionalPatent Application No. 60/789,640, filed Apr. 6, 2006, the disclosure ofwhich is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to reconstructing and paving roads. Morespecifically, the present invention is method of using a soluble sodiumsilicate composition to stabilize soil for a road base or sub-baseapplicable to the construction of new roads and the reconstruction orreinforcement of existing roads.

BACKGROUND OF THE INVENTION

Construction and maintenance of roads, especially secondary roads,requires a solid, stabilized base and sub-base on which to place theroad surface. Preparation for road paving generally includes compactionof the base or sub-base, which may comprise clay, gravel, crushed stone,and the like, either taken from the native materials or transported tothe site. Frequently, the base material includes crushed concrete andasphalt from the old road base or surface. Whether the material isprimarily reclaimed from an old road surface material, taken from a newor old base on site, or is made from materials transported to the site,maximizing the stability of the material increases the longevity of theroad surface and decreases the frequency and cost of repairs.

Soils too weak to bear the anticipated load can be stabilized by theaddition of materials which impart mechanical strength, such asaggregate, and by the addition of chemical stabilizers, which decreasewater absorption and increase the cohesion of the soil matrix by forminga cement-like compound to hold the matrix together. The appropriate typeof stabilization and results to be expected depend upon the soil typesencountered and methods of application of the stabilizer andconstruction of the road. A range of soil compositions can serve as goodroad base material, but high strength, resistance to shear, andresistance to erosion or swelling by water are required. Most nativesoils require some extent of stabilization to achieve these goals andprovide a proper material for road construction.

Failure to provide an adequately stabilized base results in frequent andexpensive repairs. Various techniques and compounds are known forstabilizing the soil or fill beneath pavement or other construction toprovide a stable, high integrity base on which to place the pavement orother construction. Materials commonly used for this purpose includelime and fly-ash mixtures, calcium chloride, sodium silicates, mixturesof molasses and fuel oil, calcium acrylate, lignin sulfonate, and othermaterials.

Chlorides are the most commonly used product for soil stabilization.Calcium chloride assists in the compactive process, making it possibleto obtain greater densities and greater strengths with normal compactiveefforts. A major limitation of calcium chloride is its narrowapplication range. If the calcium chloride solution is applied at a lessthan specific dilution ratio the effectiveness of the compound isdiminished, while application at a higher than necessitated dilutionratio causes beading on the application surface and thus preventstreatment of the target soil. Further, the widespread use of largequantities of chlorides has been shown to be environmentally harmful.Finally, chlorides are extremely corrosive on road construction andmaintenance equipment.

Resins available under various commercial names are used as soilstabilizers and typically comprise lignin sulfonate, which is aby-product of the pulp milling industry. Lignin sulfonate is alsoreferred to as “tree sap” by those skilled in the art of roadconstruction. They provide cohesion to bind soil particles together, butare primarily used when they can be incorporated into the surfacegravel.

Additives used for roadbed stabilization are disclosed by U.S. Pat. No.4,106,296 (epoxy resins), U.S. Pat. No. 4,373,958 (lime kiln dust), U.S.Pat. No. 5,577,338 (fly ash), U.S. Pat. No. 5,820,302 (silicate andcement), and U.S. Pat. No. 6,689,204 (potassium formate and cationicpolymer), all of which are incorporated herein by reference. U.S. Pat.No. 7,070,709, incorporated herein by reference, discloses various priorart compositions used for soil stabilization. Those products, however,have numerous disadvantages such as poor longevity, high cost, andenvironmental toxicity. The trade-offs are either accepting theenvironmental issues that come with products of longer useful life;dealing with a shorter lifespan for an environmentally friendly product;or paying significantly more for environmentally safe products with afavorable useful life.

A more acceptable method of roadbed stabilization is needed. It is anobject of this invention to provide an improved composition and methodof using the improved composition for soil stabilization that is botheconomical and environmentally sound.

SUMMARY OF THE INVENTION

The present invention is directed to a method of using a composition toprovide solid, stabilized, and extremely hard bases and sub-bases forroad construction. The composition is generally comprised of a solublesodium silicate which, applied at the disclosed application rate,increases aggregate base strength for a given roadway at a faction ofthe cost of existing materials. The method of the invention addressesthe application of the disclosed composition to maximize stabilizationof roadbeds. The present invention addresses drawbacks experienced withthe prior art because it provides an effective road stabilizer that isboth economical and environmentally friendly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following descriptions of the present invention have been simplifiedto illustrate elements that are relevant for a clear understanding ofthe present invention. The descriptions eliminate, for purposes ofclarity, elements found in typical soil stabilizers and detailedexplanations of procedures used in road construction. Those of ordinaryskill in the art will recognize that other elements of both thecomposition and method may be desirable or necessary to implement thepresent invention. Because such elements are well known in the art anddo not facilitate a clearer understanding of present invention, adescription of such elements may not be provided herein.

The stabilizer of the present invention comprises a non-toxic, watersoluble chemical composition used as a material stabilizer for roadbases. The disclosed stabilizer generally comprises a soluble sodiumsilicate in a water base, otherwise known as “waterglass.” The preferredembodiment of the stabilizer contemplates an aqueous solution consistingof 28-30 percent silicon dioxide by weight and 8.5-9.5 percent sodiumoxide by weight with an overall specific gravity ranging from 1.37 to1.42 and an average viscosity of 150 at 20° C. The average weight ratioof silicon dioxide to sodium oxide for the stabilizer should be between3.1 and 3.4. A commercial version of the stabilizer is available fromINEOS Silicas Americas located in Joliet, Ill. under the trade nameCrystal® 78.

Application of the stabilizer of the present invention is accomplishedby the use of conventional spray equipment known in the art of roadconstruction and maintenance. It may be gravity fed or pumped throughhoses, spray nozzles, or fixed sprayers to uniformly apply the compoundto the material to be treated. Motor-graders, asphalt grinders, mixers,pug mills, compactors, rollers, and other conventional road constructionequipment may be utilized to blend, set grade, and compact thestabilized base.

A preferred embodiment of the present invention includes the applicationof the stabilizer at three steps of the road bed construction atspecific application rates. In the preferred embodiment, it isrecommended that the road bed be laid in sections of ¼ to ½ mile inlength. Once the road bed has been leveled and the bed constructionmaterial has been windrowed along the road, the road bed is prepared byapplying stabilizer to the road bed at a rate of 20-25 gallons per mileof 24′-30′ width road surface with a depth of three inches to sixinches. The amount of water in which the stabilizer is diluted willdepend upon the type of applicator used, size of the water truck, andthe weather conditions (temperature, humidity, wind). The typicalrecommended dilution is about 55 gallons of stabilizer per 5,000 gallonsof clean water. After the initial application of the stabilizer, theroad bed should be compacted by any of the various methods known in theart of road construction.

The second step of the preferred embodiment involves applying materialfrom the windrow to the road bed in one- to two-inch lifts. As thegrader is laying material from the windrow across the road, thestabilizer is applied to the lift and then mixed into the materialplaced upon the road bed. The amount of stabilizer applied per lift willdepend upon the number of lifts to be used in the road bed construction.A total of 220 gallons of stabilizer should be used for each mile of24′-30′ width of road surface assuming a total bed thickness of three tosix inches. The amount of water used for the application of the 220gallons of stabilizer per mile will depend upon the type of applicatorused, size of the water truck, and the weather conditions. Each lift ofmixed material and stabilizer should be well mixed and compacted by anyof the methods known in the art prior to application of the next lift.This process is repeated until all lifts have been applied (windrow hasbeen completely used) and well compacted. The finish grade and slope ofthe bed should then be prepared.

The third step of the preferred embodiment is finishing off the road bedsurface with additional stabilizer. The stabilizer is applied to thefinished bed at a rate of 25-30 gallons per mile of 24′-30′ width roadsurface with a depth of three inches to six inches. Compaction of theroad surface should continue until the surface is dry. As with theprevious steps, the amount of water used to dilute the 25-30 gallons ofstabilizer will depend upon the type of applicator used, the size of thewater truck, and the weather conditions.

The preferred embodiment also contemplates keeping the working surfaceswet while compacting. The appropriate amount of moisture for workingroad compaction is well known by those in the art of road construction.It is recommended that compactors constantly work the road to maximizethe hardening provided by the stabilizer. Roadways may be furtherenhanced by the application of a sealant to protect the new road bedfrom the elements. The preferred embodiment contemplates using a surfacetreatment coating process such as the application of a bituminous chipseal, otta seal (oil/gravel mixture), cement, bituminous hot mix, or anyof the other surface treatment processes known in the art.

As road widths vary, the present invention contemplates using thefollowing total stabilizer amounts for all three steps per mile ofthree-inch to six-inch depth road at the ratios described herein:

Road Bed Surface Width (Feet) Amount of Stabilizer (Gallons) 24-30 27531-37 330 38-44 385 45-51 440

For a seven-inch road depth, the present invention contemplates usingthe following stabilizer amounts for all three steps per mile of road atthe ratios described herein:

Road Bed Surface Width (Feet) Amount of Stabilizer (Gallons) 24-30 33031-37 385 38-44 440 45-51 495

For an eight-inch road depth, the present invention contemplates usingthe following stabilizer amounts for all three steps per mile of road atthe ratios described herein:

Road Bed Surface Width (Feet) Amount of Stabilizer (Gallons) 24-30 38531-37 440 38-44 495 45-51 550

While the present invention may be used for a wide variety of aggregatemixtures comprising clay material, caliche soils, and sandy loam withlow sand content, it is recommended that the soil used in constructingthe road bed consist of a good binding material with aggregate largeenough to provide a driving surface. Examples of aggregate gradationthat provide exceptional results are provided below:

Sieve Size % Passing Example A  1″ 100 ¾″ 100 ⅜″ 65-95  #4 40-85 #1020-70 #40 10-45 #200  10-15 Example B  1″ 100 ¾″ 100 ⅜″ 50-85  #4 35-80#10 20-70 #40 10-40 #200  10-15 Example C  1″ 100 ¾″  95-100 ⅜″ 65-95 #4 40-75 #10 25-70 #40 10-45 #200  10-15 Example D ¾″ 100 #4 38-75 #822-62 #30  12-37 #200   8-15The material passing through the #200 sieve should be binding-typematerial consisting of more clay than silt (an average of 8-15 percentsilt).

Another preferred embodiment of the present invention is the use of thedisclosed stabilizer with full-depth reclamation. Full-depth reclamationis an in-place recycling alternative to road reconstruction. Areclaiming machine is used to turn an old asphalt pavement into a roadbase by uniformly pulverizing the full thickness of the old pavement andblending it with a portion of underlying material. The process for fulldepth reclamation involves three steps: the pulverization of theoriginal surface and the blending of additives and imported materials,grading and compacting the new surface, and the application of a wearingsurface. The process allows for correcting drainage and cross slopeproblems, as well as widening the roadway.

The process usually adds bituminous emulsion, chemical or mechanicalstabilization agents to enhance the strength of the new base that issealed with an asphalt friction course or a sealing treatment, dependingon expected loads. Prior art additives used in full-depth reclamationcommonly include bituminous emulsions, but they are often used incombination with chemical additives like lime, portland cement, and flyash to add strength, as well as mechanical additives like crushed stone,RAP, and sand to correct deficiencies in the existing materials. Use ofthe stabilizer of the present invention provides the same benefits aswith new road construction and eliminates the same disadvantages ofexisting stabilizers.

The steps in the preferred embodiment of full-depth reclamation aresimilar to those used in new road bed construction, but includes theinitial steps of scarifying (ripping) and pulverizing existing pavement.The depth of pulverization is usually six to ten inches, which onsecondary roads will typically include all of the surface and base, plussome part of the subgrade. To achieve the proper gradation afterpulverization, more than one pass of the equipment may be necessary. Forparticle distribution, the final pulverized material should be 100%smaller than two inches with 55% passing a No. 4 sieve. The material maybe pulverized in place, or may be removed and windrowed along the sideof the road bed for application. If the material is windrowed, the samesteps may be used as disclosed above for new road bed construction.

For in-place pulverization, once the existing pavement has beensufficiently pulverized, the material must be shaped and graded to thedesired cross-section and grade. The final base elevation requirementsmay necessitate a small amount of material removal or addition. Forin-place pulverization, once the material is properly graded, thestabilizer of the present invention is applied to the road bed at a rateof 240-245 gallons per mile of 24′-30′ width road surface with a depthof three inches to six inches. As with new roadbed construction, it isrecommended that the road bed be laid in sections of ¼ to ½ mile inlength. The amount of water in which the stabilizer is diluted willdepend upon the type of applicator used, size of the water truck, andthe weather conditions (temperature, humidity, wind). The typicalrecommended dilution is about 55 gallons of stabilizer per 5,000 gallonsof clean water. The stabilizer and pulverized pavement should then bewell mixed and compacted by any of the methods known in the art prior toapplication of the next lift. The finish grade and slope of the bedshould then be prepared.

As with new road bed construction, the preferred embodiment includesfinishing off the road bed surface with additional stabilizer. Thestabilizer is applied to the finished bed at a rate of 25-30 gallons permile of 24′-30′ width road surface with a depth of three inches to sixinches. Compaction of the road surface should continue until the surfaceis dry. As with the previous steps, the amount of water used to dilutethe 25-30 gallons of stabilizer will depend upon the type of applicatorused, the size of the water truck, and the weather conditions. Thepreferred embodiment contemplates using a surface treatment coatingprocess such as the application of a bituminous chip seal, otta seal(oil/gravel mixture), cement, bituminous hot mix, or any of the othersurface treatment processes known in the art.

The present invention may be embodied in other specific forms withoutdeparting from the spirit of any of the essential attributes thereof,therefore, the illustrated embodiment should be considered in allrespects as illustrative and not restrictive, reference being made tothe appended claims rather than to the foregoing description to indicatethe scope of the invention.

1. A method of soil stabilization for a road bed comprising: providingsoil stabilizer comprising 28-30 percent silicon dioxide by weight and8.5-9.5 percent sodium oxide by weight in an aqueous solution; applyingthe soil stabilizer to the road in three steps, the steps comprising:(i) a first step of applying the soil stabilizer to the road bed at arate of one gallon of the soil stabilizer per every 420-880 square yardsof road surface; (ii) a second step of applying a mixture of road bedmaterial and the soil stabilizer to the road bed at a rate of one gallonof the soil stabilizer per every 50-80 square yards of road surface; and(iii) a third step of applying the soil stabilizer to the road bed at arate of one gallon of the soil stabilizer per every 360-700 square yardsof road surface.
 2. The method of claim 1 wherein the road bed iscompacted after each of the steps of applying the soil stabilizer. 3.The method of claim 2 wherein the road bed is leveled before the firststep of applying the soil stabilizer.
 4. The method of claim 3 whereinthe grade and slope of the road bed is finished before the third step ofapplying the soil stabilizer.
 5. The method of claim 2 wherein the gradeand slope of the road bed is finished before the third step of applyingthe soil stabilizer.
 6. The method of claim 5 wherein the road bed iscompacted after the third step of applying the soil stabilizer until thesurface of the road bed is dry.
 7. The method of claim 6 wherein thesecond step comprises applying the mixture of road bed material and thesoil stabilizer in lifts of one to two inches in thickness andcompacting the road bed after each application of the mixture.
 8. Themethod of claim 7 wherein the soil stabilizer is diluted in a ratio ofabout one 55-gallon drum of the soil stabilizer per 5,000 gallons ofwater before the three application steps.
 9. The method of claim 1wherein the second step comprises applying the mixture of road bedmaterial and the soil stabilizer in lifts of one to two inches inthickness and compacting the road bed after each application of themixture.
 10. The method of claim 1 wherein the providing step comprisesproviding a soil stabilizer comprising about 28.4 percent silicondioxide by weight and about 8.7 percent sodium oxide by weight in anaqueous solution.
 11. A method of soil stabilization for a road bedcomprising: providing a soil stabilizer comprising 28-30 percent silicondioxide by weight and 8.5-9.5 percent sodium oxide by weight in anaqueous solution; and applying the soil stabilizer to the road bed at arate of 0.018-0.027 gallons of the soil stabilizer per square yard ofroad bed.
 12. The method of claim 11 wherein the soil stabilizer isdiluted in a ratio of about one 55-gallon drum of the soil stabilizerper 5,000 gallons of water before the steps.
 13. The method of claim 12wherein the step comprises applying the mixture of road bed material andthe soil stabilizer in lifts of one to two inches in thickness andcompacting the road bed after each application of the mixture.
 14. Themethod of claim 13 wherein the providing step comprises providing a soilstabilizer comprising about 28.4 percent silicon dioxide by weight andabout 8.7 percent sodium oxide by weight in an aqueous solution.
 15. Amethod of soil stabilization for a road bed comprising: providing a soilstabilizer comprising silicon dioxide and sodium oxide wherein theaverage weight ratio of silicon dioxide to sodium oxide is between 3.2and 3.3; applying the soil stabilizer to the road bed in three steps,the steps comprising: (i) a first step of applying the soil stabilizerto the road bed at a rate of one pound of the soil stabilizer per every95-210 square yards of road surface; (ii) a second step of applying amixture of road bed material and the soil stabilizer to the road bed ata rate of one pound of the soil stabilizer per every 12-20 square yardsof road surface; and (iii) a third step of applying the soil stabilizerto the road bed at a rate of one pound of the soil stabilizer per every80-170 square yards of road surface.
 16. The method of claim 15 whereinthe soil stabilizer is diluted in water before the steps of applying thesoil stabilizer.
 17. The method of claim 15 wherein the second stepcomprises applying the mixture of road bed material and the soilstabilizer in lifts of one to two inches in thickness and compacting theroad bed after each application of the mixture.
 18. The method of claim16 wherein the road bed is compacted after each of the steps of applyingthe soil stabilizer.
 19. The method of claim 17 wherein the road bed isleveled before the first step of applying the soil stabilizer.
 20. Themethod of claim 18 wherein the grade and slope of the road bed isfinished before the third step of applying the soil stabilizer.
 21. Akit for soil stabilization of a road bed comprising: a soil stabilizercomprising 28-30 percent silicon dioxide by weight and 8.5-9.5 percentsodium oxide by weight in an aqueous solution; and instructions for amethod of application of the soil stabilizer to the road bed, the methodcomprising: (i) a first step of applying the soil stabilizer to the roadbed at a rate of one gallon of the soil stabilizer per every 420-880square yards of road surface; (ii) a second step of applying a mixtureof road bed material and the soil stabilizer to the road bed at a rateof one gallon of the soil stabilizer per every 50-80 square yards ofroad surface; and (iii) a third step of applying the soil stabilizer tothe road bed at a rate of one gallon of the soil stabilizer per every360-700 square yards of road surface.
 22. A method of soil stabilizationfor a road bed comprising: providing a soil stabilizer comprising 28-30percent silicon dioxide by weight and 8.5-9.5 percent sodium oxide byweight in an aqueous solution; and applying the soil stabilizer to theroad bed at a rate of about 0.005 gallons of the soil stabilizer persquare yard per inch thickness of road bed.